Bundle.main.url cannot find file

I tried several answers from different posts but none of them solved my problem.

Situation I am in:

• The project is called XcodeTests and the only target it has is XcodeTests
• I have a my_file.txt file at <ProjectRoot>/XcodeTests/res/
• Upon creating my_file.txt, I made sure that target XcodeTests was selected
• Both res folder and my_file.txt exists in storage directories confirmed by Finder
• In Build Phase of XcodeTests, CopyBundleResources does include my_file.txt

The following code throws Fatal error: Couldn't find requested file:

import Foundation

guard let myFileURL = Bundle.main.url(forResource: "my_file", withExtension: "txt")
else
{
    fatalError("Couldn't find requested file")
}

What should I do so that Bundle.main.url can find my_file.txt?